The present invention generally relates to a device for transferring a workpiece into and out from a vacuum chamber which may contain a conveyor device for moving the workpiece within the chamber. More specifically, the invention relates to a device for transferring a workpiece into and out from a process/vacuum chamber of a cathode sputtering system.
The coating of substrates (or workpieces), for example, of compact disks, (CD's) is known in vacuum processing technology, particularly in thin-film technology. Compact disks are a modern storage medium for digital information. Imprinted plastic disks are sputter coated with a layer, for example, a layer of aluminum having a thickness of less than 1/10,000 mm. The sputter coating systems utilized for this purpose generally include a turntable for conveying the substrates from position-to-position within a processing/vacuum chamber of the system.
Further, a robot device may be used to load and unload the substrates to and from the system via an airlock in a clean room. The turntable is equipped with a substrate carrier and conveys the substrate from the airlock through the vacuum chamber. Sputtering ensues by means of a high power sputtering cathode constructed as a magnetron.
In German published application DE 3716498, there is disclosed a device for transferring an essentially flat workpiece into an evacuated vacuum coating chamber and for delivering and withdrawing the workpiece to and from the deposition area of a coating source for the purpose of depositing a coating on a surface of the workpiece. This reference describes a device in which a coating mechanism is arranged in an area of the coating chamber. The transfer mechanism includes one or more cover shaped workpiece carriers which are used to move the workpieces into a position adjacent a transfer opening of the coating chamber. As a result, the opening can be closed by, first, the workpiece carrier and, second, a lifting plate that is held and guided on a rotary turntable that is rotatably seated within the coating chamber. The workpiece carrier can be pressed against the opening and the top or cover of the coating chamber by lifting cylinders supported against the charging mechanism and the lifting plate can be pressed thereagainst by a lifting mechanism secured to the bottom plate.
U.S. Pat. No. 3,915,117 discloses a vacuum coating apparatus for coating various products comprising a housing which includes a fixed part and a rotatable cover part which, together, define a closed, gas sealable, housing chamber which may be evacuated. A plurality of product supports are carried on the rotatable part of the housing at spaced locations and they are movable to present them at various operating stations. One of the operating stations preferably includes a gas sealable coating chamber which is communicable with the gas sealed housing chamber and it is provided with separate means for evacuating the coating chamber. Movable sealing means are located at at least one of the stations for sealing the coating chamber and isolating it from the housing chamber. Similarly, a loading chamber is located at a separate station and is separately communicable with the housing chamber, or it may be isolated from the housing chamber and separately evacuated.
The moveable sealing means comprises a plate member engageable on a bottom side of a ring member that itself serves as a workpiece support member. The plate member is axially moveable and is used to move the ring member against an axial end of a transfer chamber opening.
The devices of the prior art exhibit several disadvantages in use.
Overall, the rotary turntable must be made so as to be extremely sturdy. A sturdy substrate carrier is also required in order to avoid sagging.
To make these items sturdy, they are made heavy and, accordingly, large masses must be conveyed during the processing cycles. Due to the corresponding high mass moments of inertia, the processing cycles sequence correspondingly slowly. Limits are therefore placed on how economical processing with such systems can be.
Yet further, the workpiece/substrate holder must be made very sturdy because the workpiece/substrate holder is subjected to high flexural stresses when the lifting mechanisms for the holder is raised and when the holder is supported or pressed against parts of the vacuum chamber.
Additionally, the cost of the individual parts is extremely high. This cost is multiplied by the plurality of substrate holders in the rotary plate.